Homeostasis - kidneys and water balance

Kidney transplant

Immunosuppressant

Medicines which prevent the immune response of the body from destroying a transplanted organ

Immune system

The body's natural defence mechanism against infectious diseases.

Rejection

The process by which the immune system of the body can reject a transplanted organ

Recipient

The person who receives a new healthy organ in a transplant operation

Stem cell

Cells which can divide repeatedly without becoming differentiated and have the capacity to develop into a diverse range of specialised cell types.

Antigen

The protein markers found on the surface of a cell that causes the immune system to produce antibodies against it.

Stroke

When a blood clot forms in the brain as a result of atherosclerosis or there is bleeding in the brain. It can be fatal.

Organ

A structure with a particular function which is made up of different tissues.

Donor

The person who donates an organ for a transplant operation

Kidney transplants

If the kidneys fail completely they may be replaced by a kidney transplant. In a transplant the functions of the failing kidneys are taken over by a single healthy kidney from a donor. The donor kidney is joined to the blood vessels and the bladder in the groin of the patient (the recipient) and shortly after a successful transplant urine begins to flow from the new kidney. If all goes well the transplanted kidney will function normally in its new body, cleaning and balancing the blood.

One kidney is enough to remove the waste urea and balance the blood of an individual for the rest of their lives. However, most transplanted kidneys only last about 9 years. Once they begin to fail again the patient will have to return to dialysis or have another transplant if a donor becomes available.

In a transplant operation the new kidney is attached to the blood vessels and bladder but the old kidneys are often left in place as well, in case they recover some of their function.

Rejection

One big problem is rejection. The protein markers (antigens) on a kidney are usually different from a patient's protein markers. The patient's immune system detects this difference and may reject the new kidney. Immunosuppressant medicines are used to suppress the immune system to prevent rejection.

Finding donors

Human organs are filled with cold fluids and transported in chilled containers to keep them healthy so they will work again once they have been transplanted.

The other big problem with kidney transplants is that there are not enough donors to go around. In the UK alone about 2500 transplants are carried out each year but there are still around 7000 people on dialysis waiting for a transplant. Most kidneys come from people who have died in an accident or have died suddenly from a stroke or similar event. Better car safety and better medicine mean fewer people are dying - good news but giving fewer donors. More healthy people are choosing to donate one of their kidneys to someone with kidney failure. They are known as living donors. In future stem cell technology may allow us to grow new kidneys for anyone who needs them.

Question 7

a) Give two reasons why the number of available donor organs has fallen in recent years.

Better car design and wearing safety belts means cars have become safer so fewer people die in accidents. There are fewer drink/drivers which has also reduced the number of fatal road traffic accidents. We have better medical treatments for strokes and heart attacks so fewer people die of sudden brain haemorrhages etc.

b) Suggest advantages and disadvantages of the current UK system of organ donation

The big advantage is that organ donation is a gift so people really want to do it and millions of people sign the register. The main disadvantage is that lots of organs are lost because people don't sign the register and doctors don't like to ask relatives at a time when they are very distressed because a member of their family is dead or dying.